Question 5
(a) State two roles each of the following hormones in animal reproduction:
(i) oestrogen;
(ii) testosterone;
(iii) oxytocin;
(iv) progesterone. (8 marks)
(b) A poultry farmer bought 1,000 point-of-lay pullets for egg production.
(i) Recommend the most suitable intensive management system for easy collection
of eggs. (1 mark)
(ii) State:
I. three advantages of the management system recommended in 5(b)(i);
(3 marks)
II. three disadvantages of the management system recommended in 5(b)(i).
(3 marks)
(c) Mention three ways by which plant nutrients are lost from the soil. (3 marks)
Observation
Question 5 was not popular among candidates.
(a) Many candidates could not state the roles of the reproductive hormones in farm animals;
(b) Most candidates do not understand Question 5(b) and many of them avoided it.
The expected answers include:
(a) Roles of hormones in animal reproduction
- Oestrogen
- Stimulates the development of female secondary sex characteristics
- Brings about ovulation/heat in female animals
- Promotes the production of eggs through oogenesis
- Prepares the uterus lining for the reception of the fertilized ovum
- Increases the blood supply as well as the water content of the uterus
- Stimulates the growth of the duct system in the mammary glands (udder)
- Increases ciliary activities and mucous secretion in the oviduct
- Induces the rapid multiplication of epithelium in the vagina
- Testosterone
- Initiates spermatogenesis/production of spermatozoa
- Responsible for the development of male secondary sex characteristics
- Maintains sex drive (libido)
- Enhances muscular and skeletal growth
- Reduces fat deposition
- Promotes the growth of accessory sex glands
- Sustains the life of sperms in the epididymis
- Oxytocin
- Aids in the contraction of the female uterine muscles during parturition
- Affects mammary gland after birth by causing milk-let down
- Promotes the transport of spermatozoa in the female genital tract
- Progesterone
- Ensures the development of the uterus and implantation of the fertilized ovum
- Inhibits oestrus/prevents heat period in female animals
- Causes the development of the alveoli in the mammary gland
- Ensures the continuance/maintenance of pregnancy
(b) (i) Most suitable intensive management system for easy collection of eggs
- Battery cage system
(ii) I Advantages of the battery cage system
- The rate of feed consumption can easily be determined
- Makes collection of eggs with clean shells possible
- Makes record keeping easy
- Easy access to feed and water
- Birds are protected from predators
- Low labour requirement
- Feed wastage is minimized
- Facilitates culling of unproductive/sick birds
- Cannibalism/ egg pecking is reduced
- Egg production is high
- Aids easy administration of drugs and vaccines
- Egg collection is easy
- Stealing of eggs/birds is reduced
- Birds are protected from adverse weather conditions
II Disadvantages of the battery cage system
- Diseases can spread easily
- Birds do not exercise which can lead to incidence of metabolic disorders
- Cost of establishment is high
- Requires high level of farm sanitation/biosecurity
- Could result in lameness
- High cost of maintenance of battery cages
- Requires technical skill to establish
(c) Ways by which nutrients are lost from the soil
- Land clearing
- Crop removal
- Soil erosion/Flooding
- Leaching as a result of water percolation and infiltration
- Oxidation and reduction reactions
- Volatilization
- Poor tillage practices
- Continuous cropping
- Burning
- Overgrazing